This handout image provided by the Texas Department of Criminal Justice shows Edgar Tamayo. Attorneys for the Mexican national on Texas death row for the slaying of a Houston police officer hoped a civil suit, challenging what they argued is an unfair and secretive clemency process in the nationâs most active capital punishment state would block the inmateâs scheduled execution this week. Tamayo, 46, was set for lethal injection Wednesday evening, Jan. 22, 2014, in Huntsville. (AP Photo/Texas Department of Criminal Justice)

Photo: HOPD

This handout image provided by the Texas Department of Criminal...

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Protesters in Edgar Tamayo's hometown of Mizcatlan, Mexico, show support for the death row inmate.

Judges in state and federal courts on Tuesday rejected a flurry of efforts to spare the life of convicted Houston cop killer Edgar Tamayo, potentially clearing the way for his execution Wednesday.

Barring a last-minute stay, Tamayo, 46, a Mexican national, is scheduled to be put to death just after 6 p.m. for the January 1994 murder of Houston policeman Guy Gaddis, who was shot in the head while preparing to transport Tamayo and another man, both handcuffed, to jail.

Tamayo's case has garnered international attention because of a violation of the United Nations' Vienna Treaty on Consular Affairs, an agreement that requires authorities to tell arrested foreign nationals that they may talk with their nations' consulates. An international court and Mexican and United States officials, including Secretary of State John Kerry, have called for a judicial review.

The killer's lawyers contend that Gov. Rick Perry, who previously declined to intervene on behalf of two other Mexican nationals with Vienna Convention issues, had pledged to provide judicial reviews in future cases.

"We are continuing to pursue our options for appeal and vindication of Mr. Tamayo's right to review of the consular rights violation in this case as promised by Gov. Perry and Attorney General Greg Abbott," Tamayo attorney Maurie Levin said in an email. "The failure of the governor and attorney general to honor their promises has tied the hands of the lower courts. It is dismaying that Texas' highest officials think so little of keeping their word."

Brain injuries

Had Tamayo been allowed to talk with Mexican officials, his lawyers said, early efforts could have been made to reach Mexican residents who could testify to serious brain injuries the killer received in a bull riding accident. Such testimony in the trial's punishment phase could have resulted in a life sentence, they argued.

Adam Aston, Texas' principal deputy solicitor general, argues that the state did not renege on its pledge. "Two years ago," he wrote in a letter to Tamayo's lawyers, "the office of the attorney general offered Mr. Tamayo a process for attempting to prove prejudice in federal court. Mr. Tamayo urged the court to reject the state's offer."

On Tuesday, the U.S. District Court for the Southern District of Texas-Houston Division told the killer's lawyers it would not revisit its rejection of an earlier mental retardation-based appeal. The court denied the appeal in March 2011, saying that it had not met the time requirements for such filings. Levin said she will appeal the ruling to the 5th U.S. Circuit Court of Appeals.

The setback in the Houston court was joined by rejections in the Texas Court of Criminal Appeals, the state's highest criminal court, and the U.S. District Court for the Western District of Texas-Austin division.

Key witness

Among key arguments rejected by the appeals court was the assertion that Jesus Martinez, the prosecution's key witness in Tamayo's trial, lied under oath about lenient sentencing he would receive for his testimony. Tamayo's lawyers said in their petition that prosecutors coached Martinez on his testimony and that the perjured testimony may have tainted the trial.

Martinez's attorney took the stand in the trial, revealing the deal, they claimed, but the details of the arrangement never came to light.

On Tuesday morning, Tamayo's lawyers offered arguments in the Austin federal court, asking Judge Lee Yeakel to bar the state pardons board from ruling on the killer's clemency petition until it ensured deliberations would be transparent and impartial.

The lawyers accused the board of violating its own rules by accepting information from police and prosecutors without giving the Tamayo team a chance to participate. They also called for board member Romulo Chavez, a former Houston policeman, to recuse himself from the case.